Fats and oils are often incorporated into raw cereal mixes preparatory to toasting. In addition, certain cereal bases, such as corn grits, wheat and oats contain a natural amount of fat, e.g., about 1% in corn grits. The fat content of such cereals, particularly those derived from corn grits, i.e., corn flakes, seriously limits the storage stability to relatively short periods of time, for example 35 days for corn flakes, thus necessitating the incorporation of antioxidants into such cereal products to prolong storage stability. The lack of storage stability is due to the development of rancidity in the cereal. Thus, such cereals now commercially available usually contain artificial additives, i.e., antioxidants, which is not desirable as far as consumer acceptance is concerned.
Commonly, commercial cereal flakes are sugar-coated. Sugar coating of cereals has been accomplished by applying sugar or sugar-containing products directly to the toasted flakes, either in the form of a powder or in aqueous solution followed by further processing to cause the sugar coating to form on the flake surface. In most processes used for this purpose, the resulting sugar-coated product is often excessively brittle. In other cases, the sugar coating becomes highly opaque and masks the cereal product. These disadvantages have resulted in less attractive cereal products which often naturally leads to less consumer acceptance. One attempt to overcome the brittleness problem caused by sugar coatings is the incorporation of edible oils in the sugar solution used for coating. The oil is used to reduce the hardness and brittleness of the sugar coated product. As an alternative, the oil is first applied to the cereal and thereafter the sugar solution is applied. U.S. Pat. Nos. 3,840,685 and 3,959,498 provide an extensive discussion of this art.
Natural, ready-to-eat breakfast cereals and snacks are produced by aggregating particulate cereal grains, primarily comprising oats, using fats and sugar syrups to preserve and agglomerate the cereal particles, using a double or single coating process. Such cereals normally include nutmeats and are prepared by mixing the base grain and nutmeat with the coating material and thereafter drying in tray driers to agglomerated sheets which are finally broken apart to provide uniformly-sized small agglomerates. In applying the coating during this process, the fat can be applied first and the sugar-coating thereafter, or the coating can be effected with a combination of fat and sugar syrup in a single-step coating operation. In one modification of this process, oven-puffed cupped rice flakes are used as one ingredient of the cereal grain mixture, as described in U.S. Pat. No. 4,038,427. The presence of the rice flakes provides a multi-textured lower density and eating quality. Such natural cereals are reputed to be storage-stable because of the high levels of sugar coating normally employed to coat the discrete particles uniformly prior to the aforesaid agglomeration step.
Puffed cereals are well-known and are usually prepared by gun-puffing or by expansion extrusion with simultaneous cutting procedures which are well-known, as described, for example, in U.S. Pat. Nos. 4,051,162; 2,954,295; and 2,954,296. Such puffed products may be prepared in any size and geometric pattern and are characterized by low density and highly porous structures. When fat and sugar-coated, such puffed products are also known to be more stable to rancidity development than uncoated identical products.
Of all of the ready-to-eat cereals, flaked cereals considerably differ from the natural cereals and from the puffed varieties in that they are of different density and an entirely different physical structure. For example, corn flakes are bubbly-surfaced continuous matrices which are highly susceptible to rancidity development, whereas natural cereals are comprised of discrete, small particles which are agglomerated and puffed cereals are low density structures characterized by a high porosity throughout. The present invention is based on the unexpected, high-order stability to rancidity which is imparted to cereal flakes by use of a substantially uniform coating of a fat on the surface of the cereal flake.